/*
===========================================================================
Copyright (C) 1999-2005 Id Software, Inc.
Copyright (C) 2006 Robert Beckebans <trebor_7@users.sourceforge.net>

This file is part of XreaL source code.

XreaL source code is free software; you can redistribute it
and/or modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of the License,
or (at your option) any later version.

XreaL source code is distributed in the hope that it will be
useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with XreaL source code; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
===========================================================================
*/
// tr_noise.c
#include "tr_local.h"

#define NOISE_SIZE 256
#define NOISE_MASK ( NOISE_SIZE - 1 )

#define VAL( a ) s_noise_perm[ ( a ) & ( NOISE_MASK )]
#define INDEX( x, y, z, t ) VAL( x + VAL( y + VAL( z + VAL( t ) ) ) )

static float    s_noise_table[NOISE_SIZE];
static int      s_noise_perm[NOISE_SIZE];

#define LERP( a, b, w ) ( a * ( 1.0f - w ) + b * w )

static float GetNoiseValue(int x, int y, int z, int t)
{
	int             index = INDEX((int)x, (int)y, (int)z, (int)t);

	return s_noise_table[index];
}

void R_NoiseInit(void)
{
	int             i;

	srand(1001);

	for(i = 0; i < NOISE_SIZE; i++)
	{
		s_noise_table[i] = (float)(((rand() / (float)RAND_MAX) * 2.0 - 1.0));
		s_noise_perm[i] = (unsigned char)(rand() / (float)RAND_MAX * 255);
	}
}

float R_NoiseGet4f(float x, float y, float z, float t)
{
	int             i;
	int             ix, iy, iz, it;
	float           fx, fy, fz, ft;
	float           front[4];
	float           back[4];
	float           fvalue, bvalue, value[2], finalvalue;

	ix = (int)floor(x);
	fx = x - ix;
	iy = (int)floor(y);
	fy = y - iy;
	iz = (int)floor(z);
	fz = z - iz;
	it = (int)floor(t);
	ft = t - it;

	for(i = 0; i < 2; i++)
	{
		front[0] = GetNoiseValue(ix, iy, iz, it + i);
		front[1] = GetNoiseValue(ix + 1, iy, iz, it + i);
		front[2] = GetNoiseValue(ix, iy + 1, iz, it + i);
		front[3] = GetNoiseValue(ix + 1, iy + 1, iz, it + i);

		back[0] = GetNoiseValue(ix, iy, iz + 1, it + i);
		back[1] = GetNoiseValue(ix + 1, iy, iz + 1, it + i);
		back[2] = GetNoiseValue(ix, iy + 1, iz + 1, it + i);
		back[3] = GetNoiseValue(ix + 1, iy + 1, iz + 1, it + i);

		fvalue = LERP(LERP(front[0], front[1], fx), LERP(front[2], front[3], fx), fy);
		bvalue = LERP(LERP(back[0], back[1], fx), LERP(back[2], back[3], fx), fy);

		value[i] = LERP(fvalue, bvalue, fz);
	}

	finalvalue = LERP(value[0], value[1], ft);

	return finalvalue;
}
